Generally, when an air bag device, which is one of a safety device, is provided in a vehicle for ensuring an occupant sitting on a seat from a traffic accident, an occupant determining device is provided at the seat in order to determine whether or not an occupant sitting on the seat exists, or whether an occupant sitting on the seat is, for example, an adult or the occupant is a child. For example, a known occupant determining device is disclosed in a Japanese Patent Laid-open Publication No.9 (1997)-207638. This occupant determining device has plural load detecting sensors and a controller. The plural load detecting sensors are respectively provided on mounting portions for mounting a seat to a vehicle floor. The controller calculates a load detection value based on detected values of each load detecting sensor and then determines whether or not an occupant sitting on the seat exists. More specifically, the controller initially calculates the load detection value by summing the detected values from each load detecting sensor by an adder, and then a determination transaction circuit being provided in the controller compares the load detection value with a predetermined threshold (a determination threshold). The controller determines whether or not the occupant sitting on the seat exists based on the foregoing compared result.
In the occupant determining, device described above, load being applied to the load detecting sensor varies due to swinging or posture variation of the occupant sitting on the seat under a traveling vehicle. Thus, in order to prevent frequent switching of an occupant determination state by temporary load variation, a low-pass filter is applied to signals transmitted from the load detecting sensors, or delaying transaction is applied at the switching of the occupant determination state by a magnitude relation between the load detection value and the determination threshold. Then the temporary switching of the occupant determination state (for example, from a state corresponding to “adult” to a state corresponding to “child”), which is generated by the swinging or the posture variation of the occupant, is prevented.
However, concerning the foregoing occupant determining device, when the delaying transaction is applied to the switching of the occupant determination state, for example even if the posture of the occupant is normalized after the occupant determination state Is switched from an actual state corresponding to an occupant actually sitting on the seat to an incorrect state being different from the actual state, the incorrect state continues for a while under the influence of the delaying transaction. That is, returning to the actual state Is delayed. Similarly, when a type of the occupant sitting on the seat is switched from the “child” to the “adult”, the state corresponding to the “child” cannot be immediately switched to the “adult”.
The present invention therefore seeks to provide an occupant determining device capable of determining immediately and accurately that an occupant sitting on a seat corresponds to “adult” in response to load applied to the seat.